Electromagnetic apparatus



I Patented Dec. 7, 1937 p UNITED STATES PATENT OFFICE 2,101,548 ELEoTRoMAcNETIc APPARATUS Carl G. Kronmiller, Minneapolis, assignor to.Minneapolis-Honcywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application May 28, 1936, Serial No. 82,217 15 Claims. (Cl. 20G-112) My invention pertains to electromagnetic apthe sleeve is a sleeve I of non-magnetic metal paratus and more particularly to electromagnetic Whose ends are overturned at I1 to clamp the switching apparatus. plates I6 firmly against the coil and to hold the In the ordinary electromagnetically operated various elements previously set forth in assem- 5 instruments wherein an element to be actuated bled relation. Extending around the coil I I on is biased to one position and is moved to a second three sides thereof is a member 20 of magnetic position by energization of a winding, it is necesmaterial, such as steel. The member 20 is formed sary for a considerable voltage drop to occur of sheet metal and is bent as shown in Figure 2 before the winding is sufficiently dcenergized for to form a U-shaped casing member which is 1c the device to return to its original position. secured to the end plates I8 through cooperating 10 Where the electromagnetic device is an electrolugs and slots 2l. The U-shaped casing member magnetically operated switch employed as a relay 20 together with the plates I6 form a magnetic in a control circuit, this may have a very decided casing around the coil enclosing the same on all disadvantage. Thus in the case of a control but one side. Member 2D terminates in two apsystem for a fluid fuel burner, such as an oil ertured lugs 23 and 24 which serve for mounting l5 burner, wherein electrical ignition means is emthe apparatus in a position such that the pasployed, it isv undesirable for a motor to remain sage through the coil is horizontal. energized after the voltage drops to the point Spaced lugs 25 and 26 are struck up from the Where the ignition means is rendered inoperative. upper leg of U-shaped member to form mount- 20 Accordingly, it becomes highly desirable in sucha ing means fora second U-shaped member'21. 20 system that the relay controlling the burner mo- U-shaped member 2 is pivotally mounted on tor and the ignition means operates on a relathe lugs and 26 through downwardly extending tively low diierential in voltage so that the relay lugs 28 and 29 and a pivot pin 30 which extends will open both the motor and ignition circuits' through lugs 25, 26, 28 and 29. One end of pin 25 before the voltage has dropped to a point where 30 is upturned as at 3I and the other end is pro- 25 the ignition means is rendered inoperative. vided with an eye 32 which serves to guide con- The object of the present invention is to provide ductors leading to a switch to be presently dea relay which will operate on such a low diiierenscribed. tial in voltage. The invention, accordingly, re- 'I'he U-shaped member 21 comprises a base sides in the various features of the switching apportion 35 and two downwardly extending legs 30 paratus by which such operation is obtained. 36 and 31 which legs are disposed on opposite Moreover, while certain features of the device are sides of the passage through coil I I. This member of particular value in such a low voltage release is made of suitable non-magnetic material, such relay, they are of general utility in any electroas brass, so as not to affect the operation of the magnetically operated device. relay. Secured to the two legs 36 and 31 is a 35 The various novel features of my electromagcore comprising a, portion 38 of magnetic material netically operated switch will be apparent from and a second portion 39 of non-magnetic maa consideration of the accompanying specificater'ial. The two portions 38 and 39 are in abuttion, claims and drawing, of whichting relationship and are held assembled by a 40 Figure 1 is a view partly in section of my imscrew I0 of non-magnetic material, such as brass, 40 proved electromagnetic apparatus, which also serves to secure one end of lthe core Figure 2 is an elevational View taken in the to leg 36. A second screw 4I secures the other direction of the arrow 2 of Figure 1, and in which end of the core to leg 31. A series of washers 43 Figure 3 is a schematic view of a control system are secured to one leg of U-shaped member 21 employing `my novel electromagnetic apparatus through a screw 44 and constitutes a weight serv- 45 as a relay. ing to bias the U-shaped member and the at- Referring to Figures 1 and 2, the winding of tached core to the position shown in Figure 1. the relay is designated by the reference numeral It will be readily seen that the magnetic center II. This winding or coil is provided with a pasof thewcore which corresponds to the center of sage therethrough in which is placed an insulatportion 38 thereof is displaced from the center 50 ing sleeve I2. Insulating washers I3 and I 6 are of coil II so that upon energization of coil II a. placed on the opposite ends of the winding. On force will be exerted tending to move core 38 to each side of the coil is an end plate I6 of suitable the right and to hence rotate member 21 in a magnetic material, such as steel. Extending counter-clockwise direction about its pivot pin through the passage of the Winding II inside 0i 30. A leaf spring, I! is secured at one end to 55 vvice by a relatively leg 3l of U-shaped member 2! and terminates at its lower end in a projecting portion it which engages the end plate it against'which it is adjacent, upon energization of the winding il. The spring i8 is preferably suiiiciently stiff that it will prevent the core 33 moving to the right suiciently tol move the leg 3l o member 2l against the end plate it. This is especially important for use with alternating current inasmuch as there is inevitably a certain uctuation in the flux to which the core is subject and if the relatively rigid leg 3l is allowed to engage with end plate it, the iluctuation in the flux will cause a chattering between leg 3l and end plate lo.

Secured on the base 35 of iJ-shaped member 2l is a clip member 5 i, which clip member serves to retain a mercury switch 52. This mercury switch 52 may be of any conventional type but is shown for purposes of illustration as comprising an en- Velope 5S of glass or similar material in which is housed spaced electrodes 5d and 55. Located within the envelope 53 at a depth to contact with said electrodes 5&2 and 55 is a quantity of mercury 5t which mercury upon switch 52' being tilted in a counter-clockwise direction is adapted to engage electrodes 5G and 55. Secured to the electrodes 'dlt and 55 are suitable conductors 53 and 5S which extend through eye 32 of pin Sil to any desired apparatus controlled by the switch. Due to the fact-that there is always an air gap between the core and the winding l the force exerted upon core 38 as the same is moved inwardly does not increase as rapidly as in the type of electromagnetically operated apparatus wherein the armature lis moved into engagement with magnetic material associated with the winding. While the pull on the core 33 does increase to some extent as the core 38 is moved inwardly,

this increase in pull is rather small. As a result only a relatively small drop in voltage below the value necessary to move core t@ sufficiently to close the mercury .switch 52 is necessary before core 38 is returned to its original position by the action of biasing washers Q3. This action is aided by the leaf spring i8 which serves to exert a force to energize the return movement of core 38 upon the complete or partial deenergization of winding il. The operation of the delow voltage dierential is also facilitated by reason of the fact that the mercury switch 52 requires a relatively small movement to open and close the same. It will further be noted that thev various advantages obtained by this apparatus are obtained through the use of a relatively simple construction, the

major portions of which are'constructed out of sheet metal stampings. In this manner an extremely cheap apparatus is afforded which operates at a relatively low voltage differential.'

In Figure 3 of the drawing, there is shown a control system employing my device as a relay to open the circuit in the event ofthe voltage of the power supply assuming a low value. In this gure, a burner motor is generally designated by the reference numeral l0. This motor may be employed for the purpose of forcing'a combustible mixture of oil to a burner nozzle from an oil burner. Designated by thereference nurneral il is any suitable ignition means.V This means the reference numeral may conveniently take the form of a high voltage spark gap, although the particular form which it takes forms no part of the present invention.

A room thermostat is generally designated by 12. This thermostat cornprises a bimetallic element decreasing, the contacts bimetallic element 55, it

- and 96.

13 to which arcatamiens g-aged with contacts 'it and i9. Contacts iii and 'lli are more widely spaced than contacts il and 'i9 so that upon deflection oithe contact arms lil and l5 tothe leit by reason of the temperature to which -bimetal element 713 is subjected l'l and lil are moved into engagement before contacts it and i8.

A step-down transformer ii@ is employed to supply low voltage power for the operation of' the control system. This transformer comprises a line voltage primary si connected to suitable line wires 32 and a low voltage secondary S3.

Designated generally by the numeral is a thermal safety switch which may be or any suitable form but is preferably of the form shown in the patent to F. S. Denison No. 1,958,081, of May S, 1934. For purposes of illustration, this switch is shown as comprising two switch arms @t and ti carrying cooperating contacts 88 and 89. Contact arm @l is biased away from contact arm `but is held in engagement therewith by a bimetallic element 9E which normally engages the underside of switch arm 8l. Upon heating of is caused to deflect to the right and if such deflection is carried sufciently far, it will move beyond switch arm 8l permitting the separation of switch arms 85 and 3l. Associated with the bimetal element 'is an electrical heating element 9|.

Generally designated by the reference numeral 93 is a stack switch which may take any usual form. Such switches normally comprise a bimetal element which extends into the stack and is operatively connected to one or more switches through a slip friction connection. For purposes of illustration, this stack switch is shown as comprising a bimetal element 55 adapted to cooperate with the xed overlapping contacts 95 The bimetal element is so constructed that it is caused to deflect to the right upon an increase in temperature and towards the left upon a decrease in temperature. When there is no combustion in the furnace, the element 9d engages 95 but upon the presence of combustion in` the furnace, the element moves into engagement with contact Qt. f

A relay is designated by the reference numeral lilll. This relay comprises na relay coil lill, and a plurality of relay arms |02, |93 and |015 which are adapted to engage contacts |05, |96 and lill, respectively. The rel-ay arms are biased away from their respective contacts and are adapted to be moved into engagement therewith through energization of relay coil Il.

The electromagnetic switch of the present inl vention is disignated by the legend Low voltage release relay, which legend indicates its function in this circuit as will be more apparrent from the following description of the operation therein. The various elements of the device bear the same reference characters as used in connection with the description of the operation lili CIA

The various elements are in the position shown when the temperature in the space heated by the burner is above the desired value. Upon a decrease in temperature occurring, contact arms 14 and 15 will be deected to the left by bimetal element 13 causing first the engagement of contacts 11 and 19. The engagement of these contacts will not however, cause the establishment of any energizing circuit. Upon the drop in temperature being carried sufliciently far, the engagement of contacts 16 and 18 will be effected. Upon such engagement taking place the following circuit will be established to relay coil IUI: from the right-hand terminal of secondary 83 through conductor IIB, contacts 19 and 11, contact arms 'I5 and 14, contacts 16 and 18, conductors III and I I2, electrode 54, mercury 56, electrode 55, conductor II3, bimetal element 94, contact 95, conductor II4, heating element 9|, conductor M5, relay coil IOI, conductor I I6, switch arm 81, contacts 89 and 88, switch arm 86, and conductor I I1 back to the left side of secondary 83. The energization of relay coil lill I02, H13 and I0@ to be moved into engagement with contacts |05, Illial and 81 against the action of the biasing means.

The engagement of switch arm 083 with contact IUE establishes the following holding circuit for relay coil lill: from the right-hand terminal of secondary 83, through conductor lill, contacts 'i9 and 11, contact arm '55, bimetal element i3, 'conductor itl, contact H86, relay arm B83, conductors S22 and M2, electrode 5ft, mercury electrode 55, conductor l i3, birnetal element iid, Contact 95, conductor 5M, heating element 9i, conductor llt, relay coil lili, conductor MG, switch arm contacts 89 and secondary 83. lt will be noted that circuit just traced is independent ci the engagement of contacts l@ and lli so that in the event ci a very slight temperature ris-e the operation of the sys-n tem will not be stopped. Due to the tact there is a greater space between contacts ld and "i8 than contacts T/i and 'JQ and due to the that the system is not placed into operation u; il contacts JG an i8 engage and is not 'placed out of oneration u contacts il and 'i9 disengage a al is provided which prevents a action or frequent starting and of burner caused by a chattering ci the thermostaat: contacts.

w e nicving into engagement of melay Mil with contact lill causes the following circuit to be established to the burner rector lfd: from one of the line wires through conductor M8, een tact lul. switch arm ldd, conductor E2G, con: ductcr l, burner motor lli and conductor l2@ to other line wire At the saine time the `following circuit to the ignition means is also established: from one ci the line wires through conductor MG, contact l-Ql, relay arin conductois and 527, ignition means "il, and conductor t28 to the other line wire The establishment oi these two circuits causes -luel to be supplied to the burner and at the saine time starts the operation of the ignition means. The result ls that under normal conditions the fuel issuing from the burner nozzle will be ignited and the furnace will be placed into ulceran tion. Upon such combustion taking place, hot gases will pass up the stack causing the bimetal element 93 to be deflected to the right in a very short space of time, causing the engagement thereof with contact 96. Upon such taking place,

causes switch arms 88, switch ari'n @t and conductor lll to the other terminal of.

kcombustion is accidentally terminated,

the following new circuit is established: from the right-hand terminal of secondary 83 through.

conductor I I0, contacts 19 and 11, contact arm 15, bimetal element 13, conductor H21, contact |06, relay arm ID3, conductors |22 and II2, electrode 54, mercury 56, electrode 55, conductor II3, bimetal element 94, contact 96, conductor I29, relay arm I02, contact !05, conductor |30, relay coil IUI, conductor II 6, switch arm 81, contacts 89 and 88, switch arm 86 and conductor II1 to the other terminal of secondary 83. Shortly after the circuit just traced is established, the bimetallic element will separate from contact 95 thus breaking the two circuits previously traced. It will be noted that the circuit just traced is independent of the heater SI so that energy is no longer supplied thereto. Thus, the bimetallic element 85 is no longer subjected to the heat therefrom and switch arms 86 and 81 remain in the position shown wherein contacts 88 and 89 are in engagement.

In the event, however, that combustion for some reason or other should not take place, hot gases will not pass up the stack and bimetal element @il of stack switch 98 will remain in the position shown in the drawing wherein it is in engagement with contact 95. The result will be that all of the current to relay coil lill continues to pass through heating element ill causing the same to eventually heat the bimetal element 98 sufficiently to cause separation of switch arms 86 and lll deenergizing the entire system. The size oi the heater 9i and the sensitivity of the binietal element El@ can loe so proportioned that switch arms and @l will he open 'after any desired period oi time. ln this manner there is an assurance that the burner will not continue in operation in event of combustion failing to take place. Moreover, inasmuch as the stack switch will return to the cold. position at any if sures the deenergization of the system at a that combustion is interrupted.

will be noted that ci the circuits through clay coil itl which have been traced "lic descr' on e' line-cl value. lli the event of this :foliage "ii a value sufficiently low f r oi the ignition means no longei i ing, the core of the relay wil ce "elea ing the mercury to separate and thus breaking all or the traced circuits thrcugh relay lill and ing the operation of the apparatus. Due relatively small diierential between the velue of voltage necessary to cause the relay to close switch 52 and that which switch is opened, it is possible to insure that the operation of the burner motor will be 'terminated before the voltage drops to a dangerously low value.

While the above described `application my electroinagnetic apparatus is one ci" the advoca- While I have shown a certain specihc embodiment of my device, it is to be understood that this is for purposes of illustration only and that my invention is to be limited only by the scope oi' the appended claims.

I claim as my invention:

1. ln combination, a winding having a passage therethrough, means for mounting said winding with said passage horizontally disposed, a rigid U-shaped member having its base portion pivotally mounted above but close to said winding with its legs extending downwardly, a core comprising magnetic material extending through said passage and secured to the legs of said U- s'haped member, means biasing said member to a position wherein `the magnetic center or" said core is displaced from the center of said wind ing, said winding being edective upon energization thereof to move said core and said member so as toicause the magnetic center of said core to approach the center of said winding, and means actuated by said member when so moved.

2. in combination, a winding having a passage therethrough, means for mounting said winding with said passage horizontally disposed, a rigid U-shaped member having its base portion pivotally mounted above but close to said winding with its legs extending downwardly, a core comprising magnetic material extending through said passage and secured to the legs or" said tlshaped member, means biasing said member to a position wherein the magnetic center of said core is displaced from the center of said winding, said winding being eiiective upon energization thereof to move said core and said member so as to causev the magnetic center of said core to approach the center of said winding, a switch associated with said member, said member being eifective upon movement thereof by the core to move said switch from one circuit controlling position to a second circuit controlling position.

3. In combination, a winding having a passage therethrough, means for mounting said winding with said passage horizontally disposed, a rigid U-shaped member having its base portion pivotally mounted above but close to-said winding with its legs'extending downwardly, a core comprising magnetic material extending through said passage and secured to the legs of said U- shaped member, means biasing said member to a position wherein the magnetic center of said core is displaced from the center of said winding, said winding being effective upon energization thereof to move said core and said member so as to cause the magnetic center of said core to approach the center of said winding, a switch havinga iiuid contact making member mounted on said U-shaped member, said member being eiective upon movement thereof by the core to change the circuit controlling position of said switch.

4. In combination, a winding having a passage therethrough, means for mounting said winding with said passagehorizontally disposed, a rigid U-shaped member having its base portion pivotally mounted above but close to said winding, a core comprising magnetic material extending Y through said passage and secured to the legs of said U-shaped member, means biasing said member to a position wherein the magnetic center of said core is displaced from the center of said winding, said winding being effective upon energization thereof to move said core and said member so as to cause the magnetic center of said core to approach the center oi said windamarga ing, means connected to said member and actuated thereby and resilient means to limit the movement of said core.

5. In combination, a winding having a passage therethrough, means for mounting said winding with said passage horizontally disposed, a rigid U-shaped member having its base portion pivotally mounted above but close to said winding, a core comprising a portion of magnetic material and a portion of non-magnetic secured together in end to end relationship, said core extending through said passage and secured at its ends to the opposite legs of said U-shaped member, means biasing said member to a position wherein the center of the magnetic portion of said core is displaced from the center of said winding, said winding being effective upon energization thereof to move said core and said member so as to cause the center of the magnetic portion of said core to approach the center of said winding, and means actuated by said member when so moved.

6. In combination, a winding having a passage therethrough, means for mounting said winding with said passage horizontally disposed, a rigid U-shaped member having its base portion pivotally mounted above but close to said winding, a core comprising magnetic material extending through said passage secured to the legs of said U-shaped member, a weight secured to one leg of said member and effective to bias said member to a position wherein the magnetic center of said core is displaced from the center of said winding, said winding being effective upon energization thereof to move said core and said member so as to cause the magnetic center of said core to approach .the center of said winding, and means actuated by said member when so moved.

'l'. in combination, a Acoil having a passage therethrough, end 'plates on opposite sides of said coil, a U-shaped member of sheet material extending around said coil and secured to said plates to form with the latter a casing for said coil, a second rigid U-shaped member pivotally mounted on said rst member, a core extending through said passage and secured to the opposite legs of said second U-shaped member, said coil being eiective upon energization thereof to cause movement of said core and consequently said member, and means actuated by such movement.

8. In combination, a coil having a passage therethrough, perforated end plates on opposite sides of said coil with their perforations in alignment with said passage, a sleeve extending through said passage and having its ends bent over and overlying said plates to clamp the same againstsaid coil, a U-shaped member of sheet material extending around said coil and secured t`o said plates to form with the latter a casing for said coil, said member having portions struck outwardly to provide spaced lugs, a second U-shaped member pivotally secured to said lugs and disposed with the legs thereof opposite said passage, a core comprising magnetic material extending through said passage, and secured to the opposite legs of said second U-shaped member, and means to be 'actuated associated with said second U-shaped member.

9. 1n combination, a coil having a passage therethrough, perforated end plates on opposite sides of said coil with their perforations in alignment with said passage, a sleeve extending through said passage and having its ends bent over and overlying said plates to clamp the same against said coil, a U-shaped member of sheet material extending around said coil and secured to amitie 'through said passage and secured to the opposite legs of said second U-shaped member, said coil being effective upon energization thereof to move said core and to rotate said second member about its pivot, and a switch movable between two circuit controlling positions upon tilting thereof mounted on said member.

10. In combination, a winding having a passage therethrough, means for mounting said winding with said passage horizontally disposed, a core comprising magnetic material, means for mountu ing said core for movement in said passage substantially longitudinally thereof, means biasing said core to a position wherein the magnetic center' of said core is displaced from the center oi said winding, said winding being effective upon energization thereof to move said core so as to cause the magnetic center of said core to approach the center of said winding, yieldable means to limit the movement of said core due to energization of said coil, and means actuated by said core when so moved.

11. In combination, a winding having a passage therethrough, means for mounting said winding with said passage horizontally disposed, a core comprising magnetic material, means for mounting said core i or movement in said passage substantially longitudinally thereof, means biasing said core to a position wherein the magnetic center of said core is displaced from the center of said winding, said winding being eiective upon energization thereof to move said core so as to Cause the magnetic center of said core to approach the center of said winding, yieldable means to limit the movement of said core due to energization of said coil, said yieldable means being ineffective until said core has moved to substantially its normal energized position, and means actuated by said core when so moved.

12. In a low voltage release relay, a winding having a passage therethrough, means for mounting said winding with said passage horizontally disposed, a core comprising magnetic material', means for mounting said core for movement in said passage substantially longitudinally thereof, means biasing said core to a position wherein the y magnetic center of said core is displaced from the center of said winding, said winding being effective upon energization thereof to move said core so as to cause the magnetic center of said core to approach the center of said winding, yieldable means to limit the movement of said core due to energization of said coil, and a switch actuated from a first to a second circuit controlling position by movement of said core.

13. In a low voltage release relay, a winding having a passage therethrough, means for mounting said winding with said passage horizontally disposed, a core comprising magnetic material, means for mounting said corer for movement in said passage substantially longitudinally thereof, means biasing said core to a position wherein the magnetic center of said core is displaced from the center of said winding, said winding being effective upon energization thereof to move said core so as to cause the magnetic center of said core to approach the center of said winding, yieldable means to limit the movement of said core due to energization of said coil, and a switch actuated from a rst to a second circuit controlling position by movement of said core, said yieldable means being ineective until said core vhas moved to substantially its energized position whereby the voltage required to hold said switch in its second circuit controlling position is not greatly 'less than that required to move it to said position.

le. In combination, a Winding having a passage therethrough, means for mounting said winding with said passage horizontally disposed, a rigid U-shaped member having its base portion pivotally mounted above said winding, a core comprising magnetic material extending through said passage and secured to the legs oi said U- shaped member, means biasing said member to a position wherein the magnetic center of said core is displaced from the center of said winding, said winding being effective upon energization thereof to move said core and said member so as to cause the magnetic center of said core to approach the center of said winding, means connected to said member and actuated thereby, and resilient means to limit the movementA of said core, said resilient means comprising a leaf spring element and an abutment element adapted to cooperate therewith, one of said elements being xed relative to said Winding and the other being carried by one of the legs of said U-shaped member, said abutment and said leaf spring being so spaced that they do not engage until said core has moved to substantially its energized position.

15. In a low voltage release relay, a winding having a passage therethrough, means for mounting said winding with said passage horizontally disposed, a rigid U-shaped member having its base portion pivotally mounted above said winding, a core comprising magnetic material extending through said passage and secured to the legs of said U-shaped member, means biasing said member to a position wherein the magnetic center of said core is displaced from the center of said Winding, said winding being Veiiective upon energization thereof to move said core and said member so as to cause the magnetic center of said core to approach the center of said winding, a switch associated with said member and movable from a rst to a second circuit controlling position upon movement of said core to its energized position, and resilient means to limit the movement of said core, said resilient means consisting of a leaf spring element and an abutment element adapted to cooperate therewith, one of said elements being xed relative to said winding and the other being carried by one of the legs of said U-shaped member, said abutment and said leaf spring being so spaced that they do not engage until said core has moved to substantially its energized position.

CARL G. KRONMIILER. 

